📈 Percentage Increase Calculator

What This Calculator Does

This calculator finds the percentage change between two numbers — how much something grew or shrank, expressed as a percent. Enter a starting value and an ending value, and it tells you the increase or decrease as a percentage. It is the right tool whenever you need to answer questions like “my rent went from $1,200 to $1,380 — what percent increase is that?” or “sales fell from 500 to 425, how much did I lose?”

The thing people get wrong about percentage change is which number to divide by. The change is always measured against the original value, not the new one. This calculator handles that automatically, so you never have to second-guess the direction of the division.

The Math, in Plain Terms

Percentage change is the difference between the two numbers, divided by the original number, turned into a percent. If your rent rises from $1,200 to $1,380, the difference is $180. Divide that by the original $1,200 and you get 0.15, which is a 15% increase. The same formula handles decreases: if it works out negative, the value went down.

Here is the part worth burning into memory: you divide by where you started, not where you ended up. Dividing $180 by the new $1,380 would give you about 13%, which is wrong. That single mistake — using the new value as the base — is behind a huge share of percentage errors people make, and it is exactly what this tool prevents.

A Mistake Worth Avoiding: Percentage Points

There is a subtle trap that even careful people fall into. Suppose an interest rate moves from 4% to 6%. That is a 2 percentage-point increase, but it is a 50% relative increase, because 2 is half of the original 4. These are completely different statements, and confusing them can make a change sound far smaller or far larger than it really is.

This calculator gives you the relative percentage change — the 50% figure in that example. When you are reading a number elsewhere, always check whether someone means percentage points or a relative percent change, because the gap between the two is often enormous and occasionally deliberate.

Frequently Asked Questions

How do I calculate a percentage increase?

Subtract the original value from the new value, divide the result by the original value, and multiply by 100. Going from 80 to 100 is a difference of 20; divided by the original 80 that is 0.25, or a 25% increase. The calculator above does this instantly.

Why do I divide by the original number?

Because percentage change measures growth relative to your starting point. Dividing by the new value would answer a different, less useful question and give you the wrong figure. The original value is always the base.

How do I handle a decrease?

Use the same formula — the result simply comes out negative, signalling a drop. Going from 100 to 75 is a difference of -25 over the original 100, which is a 25% decrease.

What is the difference between percent change and percentage points?

A move from 4% to 6% is 2 percentage points but a 50% relative increase. Percentage points are the raw difference between two percentages; percent change measures that difference relative to the starting value. They are not interchangeable.